WO2000015289A1

WO2000015289A1 - Splittable catheter

Info

Publication number: WO2000015289A1
Application number: PCT/US1999/021027
Authority: WO
Inventors: Bryan G. Davis; Kevin G. Tingey; Mark A. Crawford
Original assignee: Becton, Dickinson And Company
Priority date: 1998-09-15
Filing date: 1999-09-14
Publication date: 2000-03-23
Also published as: AU5822699A

Abstract

This invention relates to a splittable device incorporating at least one preferential tear line. The preferential tear line is formed by extruding a stripe of material in the main body portion of the device. The material used for the stripe and the material that is used to form the main body portion of the device have different properties. For example, each material can have similar melt and flow properties and a cohesive strength greater than the adhesive strength therebetween. Alternatively, the material used for the stripe may have a cohesive strength that is lower than the cohesive strength of the material that it used to form the main body portion of the device and that is lower than the adhesive strength therebetween but with each material still having similar melt and flow properties.

Description

SPLITTABLE CATHETER

Background of the Invention

This invention relates generally to devices that are splittable. More particularly, this invention relates to splittable devices in the field of medical devices. Even more particularly this invention relates to splittable devices in the field of medical devices for use in infusion therapy such as catheters and catheter introducers.

Catheters, particularly intravenous (IV) catheters, are used for directing fluid into or withdrawing fluid from a patient. The most common type of IV catheter is an over the needle peripheral IV catheter. As its name implies, an over the needle catheter is mounted over an introducer needle having a sharp distal tip. The catheter and the introducer needle are assembled so that the distal tip of the introducer needle extends beyond the distal tip of the catheter. The resulting assembly is inserted through the patient's skin into a peripheral blood vessel, i.e a smaller blood vessel that is not connected directly to the heart but is one of the branches of the central blood vessels that is directly connected to the heart. Once placement of the assembly in the blood vessel is verified by flashback of blood in the needle and in a flashback chamber located at the proximal end of the needle, the needle is withdrawn leaving the catheter in place. Peripheral IV catheters tend to be relatively short, and are on the order of about one and one-half inches in length. Such catheters are used to infuse fluid such as normal saline solution, various medicaments and parenteral nutrition to treat the patient in whom the catheter is placed.

Another type of IV catheter is a peripherally inserted central catheter (PICC). This catheter is substantially longer than a standard peripheral IV catheter. It is placed in a peripheral blood vessel but is advanced through the vasculature so that typically the distal tip of the catheter is in one of the central blood vessels such as the superior vena cava and is adjacent to the heart. PICCs are typically used for extended infusion therapy protocols. In order to place a PICC into a patient, a catheter introducer is used because a typical PICC does not have sufficient column strength to be inserted into a blood vessel in the same way that a standard peripheral IV catheter is placed in a blood vessel.

A catheter introducer typically is a polymeric tubular member having a hub at its proximal end to facilitate manipulation of the device. The catheter introducer is used with an introducer needle in much the same manner that a standard over the needle peripheral IV catheter is used with an introducer needle. Thus the catheter introducer is located coaxially over the introducer needle with the distal end of the introducer needle extending distally beyond the distal end of the catheter introducer. The catheter introducer and introducer needle assembly is placed into a peripheral blood vessel in much the same manner that a standard over the needle peripheral IV catheter is placed into a patient's blood vessel. When the catheter introducer and introducer needle assembly is properly located in the appropriate blood vessel, the introducer needle is removed from the catheter introducer. A PICC may then be inserted through the catheter introducer and advanced through the vasculature into its proper location. Alternatively, a guidewire may be inserted through the catheter introducer first so that when the PICC is inserted over the guidewire and through the catheter introducer, the guidewire acts as a track for the PICC to facilitate proper placement of the PICC. Once the PICC is properly placed in the vasculature, the catheter introducer is removed from the patient leaving only the PICC behind.

In order to remove the catheter introducer from the patient with a PICC inserted therethrough, the catheter introducer must be split into two pieces in order for it to be removed from the patient. The catheter introducer cannot be simply withdrawn proximally over the PICC because the PICC typically has a proximal hub or other configuration adjacent to its proximal end that is larger than the internal diameter of the catheter introducer. Thus when the distal end of the PICC is inserted into the patient through the catheter introducer, the proximal hub on the catheter introducer blocks the proximal withdrawal of the catheter introducer from the PICC. The solution to this problem is to have the body of the catheter introducer formed with longitudinally extending preferential tear lines that facilitate the splitting of the catheter introducer into two pieces. Preferably two longitudinally extending preferential tear lines are used that are generally about 180 degrees apart or at least substantially displaced from one another. When the catheter introducer is split into two pieces, the catheter introducer can be easily removed from the patient around the PICC. These preferential tear lines have in the past been formed by skiving, i.e. cutting the preferential tear lines into the exterior of the tubular body of the catheter introducer by a knife or some sharp blade or by providing longitudinal molecular orientation of the tubular body. Such longitudinal molecular orientation can be achieved, for example, by using polytetrafluoroethylene as the material for the tubular body and extruding the material in a longitudinal direction. Although such processes typically work for their intended purposes, problems do exist if the tubular body is formed using either of these processes.

The distal portion of the catheter introducer is preferably formed with a taper having a particular configuration. Such a taper is typically used for standard peripheral over the needle IV catheters and is disclosed in U.S. Patent 4,588,398. This configuration facilitates insertion of the catheter or the catheter introducer into the patient and minimizes peel back or other deformation along the distal portion of the catheter or catheter introducer that could result in patient discomfort. Various processes can be used to form such a tapered distal portion. However, a particularly preferred process is disclosed in U.S. Patent 4,661 ,300. This process involves the following steps: placing a blank, i.e. a tube that will be used as the catheter or catheter introducer, onto a mandrel, heating at least the distal tip of the blank, engaging the mandrel with a die having the shape desired for the distal portion of the catheter or catheter introducer, removing the die from engagement with the mandrel and removing the tipped blank from the mandrel.

Although this process forms the desired tapered distal portion on the catheter introducer, the process melts, and thus eliminates, the skive on the blank at least along the distal portion of the catheter introducer. In addition, if molecular orientation of the catheter introducer is used to provide the preferential tear lines, heating the tubular body disrupts this longitudinal molecular orientation. This results in a catheter introducer having no preferential tear line or at least no preferential tear line along its distal portion. Thus the catheter introducer cannot be easily split into two completely separate pieces. This makes it difficult for the clinician to remove the catheter introducer from the patient during the PICC insertion procedure.

Summary of the Invention

It is therefore an object of the invention to provide a splittable device.

It is another object of the invention to provide a splittable tubular device.

It is yet another object of the invention to provide a splittable tubular medical device.

It is still another object of the invention to provide a splittable tubular medical device that has at least one longitudinally extending preferential tear line that extends along at least the distal portion of the device.

It is an even further object of the invention to provide a process for manufacturing a splittable tubular medical device that allows at least one preferential tear line to be formed in and to remain in the distal portion of the medical device even where the distal portion of the medical device is heated to form a tapered distal portion.

In the preferred emodiment, the splittable medical device of this invention includes a main body portion in the form of a tube. The tube includes at least one and preferably a plurality of longitudinally extending preferential tear lines. These preferential tear lines are provided by incorporating stripes of material having certain different characteristics from the material used to form the major portion of the main body portion.

The stripe material that is used to form the preferential tear lines is chosen so that its cohesive strength is similar to the cohesive strength of the base material that is used to form the major portion of the main body portion but is greater than the adhesive strength between the stripe material and the base material. Thus any splitting force applied to the tube will cause the tube to split at the interface between the stripe material and the base material. Alternatively, the stripe material is chosen so that its cohesive strength is less than the cohesive strength of the base material and is less than the adhesive strength between the stripe material and the base material. In this case, any splitting force applied to the tube will cause the tube to split along the stripe material. As used herein, the term cohesive strength refers to the strength of the material whereas the term adhesive strength refers to the strength of the bond between two materials.

In addition, the stripe material preferably has melt and flow properties similar to those of the base material so that mixing or blending of the materials are controllable. By requiring both materials to have similar melt and flow properties, one material will not flow substantially into the other material when the materials are extruded into a tube or other configuration or when the distal portion of the tube is tipped. This ensures that the materials adhere to one another yet preserves the integrity of the preferential tear line along the distal portion of the tube. The stripe material should preferably extend substantially completely through the radial dimension of the tube from the inner surface thereof to the outer surface thereof.

A hub is connected to the proximal end of the tube. The preferential tear lines should be longitudinally aligned with the hub so that when the hub is pulled apart, the force applied to the hub is transmitted to the tube along the preferential tear lines to split the tube and attached hub into two separate pieces. The splittable medical device of this invention is formed by co-extruding the stripe material and the base material to form a tube or other configuration having desired dimensions such as diameter and wall thickness. For example, the main portion of the tube can be extruded from a first suitable polymer such as polyethylene, polytetrafluoroethylene or polyurethane and the stripe can be extruded from a second suitable polymer such as nylon, silicone thermoplastic copolymer, styrene-butadiene copolymer polypropylene or styrene ethylene butadiene styrene copolymer. Next the tube is cut to the appropriate size. Preferably at least two stripes are formed in the tube to provide two preferential tear lines. The tube is then connected to a suitable hub that is aligned with the stripe material forming the longitudinally extending preferential tear lines. Next, the distal portion of the splittable medical device of this invention is tipped. This is done by placing the tube over a mandrel, heating the distal end of the tube to a suitable temperature so the distal portion of the tube is flowable, advancing a die into engagement with the distal portion of the mandrel to form the desired shape along the distal portion on the tube, removing the die from contact with the mandrel and removing the tipped tube from the mandrel.

The splittable device of this invention can also be used in connection with a different type of catheter introducer. See for example, U.S. Patent 4,840,613. Such a catheter introducer is formed as a protective tubular sheath surrounding the catheter. The proximal ends of the protective tubular sheath and the catheter are fixed to a proximal hub. A stylet extends through the lumen of the catheter and is connected at its distal end to an introducer needle and at its proximal end to a stylet hub. The distal end of the introducer needle extends beyond the distal end of the catheter. A wing is located along a distal portion of the catheter and provides a mechanism for the clinician to grasp the catheter and introducer needle which facilitates the introduction of the distal end of the catheter into the patient. Once the distal end of the catheter is properly located in a patient's vein, the stylet and needle are removed from the catheter by pulling the stylet proximally via the stylet hub. A lock is located at the proximal end of the wing to hold the protective tubular sheath in place. By pulling the distal end of the protective tubular sheath distally, both the protective tubular sheath and the catheter are moved distally. As the protective tubular sheath is moved distally, it passes through the lock which facilitates the splitting of the protective tubular sheath from around the catheter. The catheter extends past the lock and the wing. This causes the catheter to be advanced into the patient's vasculature and maintains the catheter in a sterile condition. Once the catheter is moved to the proper location in the patient's vasculature, the protective tubular sheath can be locked in place which will also lock the catheter in position relative to the protective tubular sheath.

The above and other objects and advantages of the invention will be apparent upon consideration of the following detailed description.

Brief Description of the Drawings

The preferred embodiments are illustrated in the drawings in which like reference numerals refer to like elements and in which:

FIG. 1 is a perspective view of a catheter introducer using the splittable device of this invention and an associated introducer needle used therewith;

FIG. 2 is a cross sectional view taken along line 2-2 of FIG. 1 of a catheter introducer using the splittable device of this invention;

FIG. 3 is a cross sectional view of a catheter introducer using the splittable device of this invention similar to FIG. 2 but after the catheter introducer has been split into two pieces showing one mechanism by which the catheter introducer has been split along the preferential tear lines;

FIG. 4 is a cross sectional view of a catheter introducer using the splittable device of this invention similar to FIG. 3 but showing a second mechanism by which the catheter introducer has been split along the preferential tear lines; FIG. 5 is a perspective view of a catheter introducer using the splittable device of this invention after a PICC has been inserted therethrough and the catheter introducer has been partially split along the preferential tear lines;

FIG. 6 is a perspective view of a catheter introducer using the splittable device of this invention after a PICC has been inserted therethrough and the catheter introducer has been completely split along preferential tear lines;

FIG. 7 is a schematic representation of the apparatus that is used to form a tapered distal tip for a catheter introducer using the splittable device of this invention;

FIG. 8 is a perspective view of the distal portion of another catheter introducer using the splittable device of this invention; and

FIG. 9 is a perspective view of the entire device shown in FIG. 8.

Detailed Description of the Invention

As used herein, the term "proximal" refers to a location on the splittable device of this invention closest to the person using the device. Conversely, the term "distal" refers to a location on the splittable device of this invention farthest from the person using the device.

Although the splittable device of this invention is described herein as being a splittable catheter introducer that is particularly adapted for use in facilitating the insertion of a PICC into a patient, it is to be understood that this invention has applicability to catheters in general and to other medical devices that are splittable. In addition, it is to be understood that this invention has applicability to splittable devices outside of the medical device field and to splittable devices having a cross-section that is not necessarily cylindrical.

The catheter introducer 10 using this invention includes a main body portion in the shape of a tube 11 and a hub 15 connected to tube 11 at its proximal end. Hub 15 includes a pair of wings 16 on substantially opposite sides of hub 15. Wings 16 facilitate splitting of catheter introducer 10 as described in more detail below. Catheter introducer 10 may be used in conjunction with an introducer needle 20 which includes a cannula 21 and a hub 25 located at its proximal end. Hub 25 can include a flashback chamber and a vent plug located within the open proximal end of the flashback chamber to allow blood to flash back into the flashback chamber when the distal end of cannula 21 is properly inserted into a vein. Catheter introducer 10 is located about introducer needle 20 such that tube 11 is coaxially disposed about cannula 21. In this arrangement the sharp distal end of cannula 21 is located distal of the distal end of tube 11. This configuration facilitates the introduction of the distal end of tube 11 and cannula 21 into a patient's vein since the leading edge of the combination is the sharp distal tip of cannula 21.

To ease the insertion of tube 11 into a patient's vein, it is important that the distal end of tube 11 has a particular tapered configuration so that tube 11 can easily follow the sharp distal tip of cannula 21 past the patient's skin and subcutaneous tissue and into the patient's vein. U.S. Patent 4,588,398 discloses a preferred tapered configuration for the distal portion of tube 11. The disclosure of U.S. Patent 4,588,398 is hereby specifically incorporated into this specification by reference.

Tube 11 also includes a first set of preferential tear lines. This set includes at least one, and preferably two, longitudinally extending preferential tear lines 12 extending along tube 11. These preferential tear lines 12 are weakened portions of tube 11 that allow tube 11 to be split along these lines. Preferential tear lines 12 are stripes of material that have different characteristics than the material that is used to form the main body portion 13 of tube 11. This stripe material adheres to the base material to form an integral unit. The material that is used for the stripes that form the preferential tear lines 12 is chosen so that its cohesive strength and the cohesive strength of the base material that is used to form main body portion 13 are both greater than the adhesive strength between the stripe material and the base material. Thus any splitting force applied to tube 11 will cause tube 11 to split at the interface between the stripe material and the base material. Alternatively, the stripe material is chosen so that its cohesive strength is less than the cohesive strength of the base material and is less than the adhesive strength between the stripe material and the base material. In this case, any splitting force applied to tube 11 will cause tube 11 to split along the stripe material. In addition, the stripe material and the base material should have similar melt and flow properties so that mixing or blending of the materials are controllable. By requiring both materials to have similar melt and flow properties, the materials will remain sustantially separate so that one material will not flow significantly into the other material when the materials are extruded into a tube or other configuration or when the distal portion of tube 11 is tipped. This ensures that the materials adhere to one another yet preserves the integrity of preferential tear lines 12 along the distal portion of tube 11.

For example, a first suitable polymer such as polyethylene, polytetrafluoroethylene or polyurethane can be used to form main body portion 13 of tube 11. These materials are biocompatible, sterilizable and have appropriate mechanical properties for use in a catheter. A second suitable polymer that provides the necessary strength, melt and flow characteristics includes nylon, silicone thermoplastic copolymer, styrene-butadiene copolymer, propylene and styrene ethylene butadiene styrene copolymer. This second material forms the striped portion of tube 11.

An alternate mechanism for controlling the relative cohesive strengths of the base mateπal and the stripe material and the adhesive strength between these two materials is to use the same material for the stripe and the base but to process the two materials differently. For example, fillers or oils could be added to either the stripe material or the base material. In addition, one or both of the stripe material and the base material could be processed as a foam.

The stripes of preferential tear lines 12 preferably extend along substantially the entire longitudinal length of tube 11 and preferably extend substantially completely radially through tube 11 from the inner surface thereof to the outer surface thereof. It is possible to have stripes that do not extend completely radially through tube 11. Such a configuration creates a line of weakness along the stripe to provide a preferential tear line. This configuration is not preferred because complete and easy splitting of tube 11 can not be ensured.

Preferential tear lines 12 allow a clinician to grasp wings 16 and pull wings away from the axis of hub 15 to tear tube 11 into two separate pieces. In one embodiment, two preferential tear lines 12 are formed substantially on opposite sides of tube 11 so they are about 180 degrees apart. In this way, tube 11 can be split in half. Although this 180 degree separation for preferential tear lines 12 is preferred, preferential tear lines 12 could be located closer together as long as they are oriented on tube 11 so that tube 11 can be separated into two separate pieces. Hub 15 and especially wings 16 should be properly oriented with respect to preferential tear lines 12 so that each wing 16 is disposed between each preferential tear line 12 and does not overlap with either of preferential tear lines 12. In this way, when each wing 16 is grasped and pulled apart, the force on each wing 16 will be transmitted along preferential tear lines 12 to split tube 11 into two pieces. Furthermore, neither wing 16 will interfere with preferential tear lines 12 during the splitting process.

Alternatively, and preferably, a plurality of preferential tear lines 12 is formed around the circumference of tube 11. For example, six preferential tear lines 12 could be formed equiangularly around the circumference of tube 11. Where six preferential tear lines 12 are used, preferably each wing 16 should extend less than about 120 degrees around the circumference of tube 11. Such an arrangement facilitates manufacture of catheter introducer 10 because the need to orient wings 16 and tube 11 in one particular orientation is eliminated. This is because the center of each wing 16 can be located about tube 11 substantially 180 degrees apart with the result that each wing 16 will be located between two preferential tear lines 12 no matter what the angular orientation between wings 16 and tube 11 is. And neither wing 16 will interfere with those two preferential tear lines 12 during the splitting process. The process of producing catheter introducer 10 will now be described. First, a tube having the desired lumen diameter and wall thickness is extruded from a first suitable polymer such as polyethylene, polytetrafluoroethylene or polyurethane that will comprise the major portion of the tube and a second suitable polymer such as nylon, silicone thermoplastic copolymer, styrene- butadiene copolymer, polypropylene, and styrene ethylene butadiene styrene copolymer that will comprise the striped portion of the tube. At least two, and preferably six, stripes of the second polymer are extruded equiangularly about the circumference of the tube. These stripes result in preferentially extending tear lines 12. Next the tube is cut to the appropriate size. The resulting tube 11 is then connected to a suitable hub 15. Hub 15 is oriented on the tube in such a manner that wings 16 on hub 15 are substantially opposed to one another so that each wing 16 is located between two preferential tear lines 12. Thus when wings 16 are pulled apart, the force applied to wings 16 is transmitted to tube 11 along preferential tear lines 12 to split tube 11 into two separate pieces.

The distal portion of tube 11 is also tipped. The tipping process is described in detail in U.S. Patent 4,661 ,300, the disclosure of which is specifically incorporated into this specification by reference. In this process, tube 11 is placed on a mandrel. A die having an interior molding surface, which is tapered according to the desired shape for the distal portion of the tube, is aligned axially with the mandrel. The distal portion of the tube is heated, typically using RF energy, so that it is flowable. The mandrel and die are brought together so the distal edge of the mandrel engages the tapered portion of the die. This action cleanly forms a smooth and uniform tapered distal portion for the tube.

FIGS. 8 and 9 disclose another use for the splittable device of this invention. These FIGS, show the splittable device of this invention used in connection with a different type of catheter device 100. Catheter device 100 includes a protective tubular sheath 110 surrounding a catheter 120. The proximal ends of protective tubular sheath 110 and catheter 120 are fixed to a proximal hub 130. A stylet (not shown) extends through the lumen of catheter 120 and is connected at its distal end to an introducer needle 140 and at its proximal end to a stylet hub 145. The distal end of introducer needle 140 extends beyond the distal end of catheter 120. A wing 150 is located along a distal portion of catheter 120 and provides a mechanism for the clinician to grasp catheter 120 and introducer needle 140 which facilitates the introduction of the distal end of catheter 120 into the patient. Once the distal end of catheter 120 is properly located in a patient's vein, the stylet and introducer needle 140 are removed from catheter 120 by pulling the stylet proximally via stylet hub 145. A lock 160 is located at the proximal end of wing 150 to hold protective tubular sheath 110 in place. By pulling the distal end of protective tubular sheath 110 distally, both protective tubular sheath 110 and catheter 120 are moved distally. As protective tubular sheath 110 is moved distally, it passes through lock 160 which facilitates the splitting of protective tubular sheath 110 from around catheter 120. Catheter 120 extends past lock 160 and wing 150. This causes catheter 120 to be advanced into the patient's vasculature and maintains catheter 120 in a sterile condition. Once catheter 120 is moved to the proper location in the patient's vasculature, protective tubular sheath 110 can be locked in place which will also lock catheter 120 in position relative to protective tubular sheath 110.

Thus it is seen that a device is provided that has longitudinally extending preferential tear lines that facilitate the splitting of the device into two separate pieces. A process is also provided for manufacturing a such a device that allows the preferential tear lines to be formed in and to remain in the distal tip of the device even where the distal tip of the medical device is heated to form a tapered distal tip.

Claims

We claim:

1. A device, comprising a main body portion defining a first surface and a second surface and having a distal portion and a proximal portion wherein the main body portion is formed from a first polymeric material having a first cohesive strength and wherein the main body portion includes at least one longitudinally extending preferential tear line formed from a second polymeric material having a second cohesive strength such that the first polymeric material adheres to the second polymeric material with a defined adhesive strength and the second cohesive strength is less than both the first cohesive strength and the adhesive strength.

2. The device of claim 1 wherein the first polymeric material and the second polymeric material each have similar melt and flow characteristics.

3. The device of claim 2 wherein second polymeric material forming the longitudinally extending preferential tear line extends from the first surface to the second surface.

4. The device of claim 2 wherein the main body portion has six longitudinally extending preferential tear lines formed therein.

5. The device of claim 2 wherein the first polymeric material is selected from the group consisting of polyethylene, polytetrafluoroethylene and polyurethane.

6. The device of claim 5 wherein the second polymeric material is selected from the group consisting of nylon, silicone thermoplastic copolymer, styrene-butadiene copolymer, polypropylene and styrene ethylene butadiene styrene copolymer.

7. A device, comprising a main body portion defining a first surface and a second surface and having a distal portion and a proximal portion wherein the main body portion is formed from a first polymeric material having a first cohesive strength and wherein the main body portion includes at least one longitudinally extending preferential tear line formed from a second polymeric material having a second cohesive strength such that the first polymeric material adheres to the second polymeric material with a defined adhesive strength and the first cohesive strength and the second cohesive strength are each higher than the adhesive strength.

8. The device of claim 7 wherein the first polymeric material and the second polymeric material each have similar melt and flow characteristics.

9. The device of claim 8 wherein second polymeric material forming the longitudinally extending preferential tear line extends from the first surface to the second surface.

10. The device of claim 8 wherein the main body portion has six longitudinally extending preferential tear lines formed therein.

11. The device of claim 8 wherein the first polymeric material is selected from the group consisting of polyethylene, polytetrafluoroethylene and polyurethane.

12. The device of claim 11 wherein the second polymeric material is selected from the group consisting of nylon, silicone thermoplastic copolymer, styrene-butadiene copolymer, polypropylene and styrene ethylene butadiene styrene copolymer.

13. A process for forming a splittable tubular device, comprising: forming a tube having a main body portion formed from a first polymeric material having a first cohesive strength and at least one longitudinally extending preferential tear line formed from a second polymeric material with a second cohesive strength adhered to the first polymeric material with a defined adhesive strength wherein the tube has an internal surface, an external surface, a distal portion and a proximal portion; placing the tube on a mandrel having a proximal portion and a distal portion; heating at least the distal portion of the tube; engaging the mandrel with a die to form a tapered configuration along the distal portion of the tube; and removing the shaped tube from the die and mandrel.

14. The process of claim 13 wherein second polymeric material forming the longitudinally extending preferential tear line extends from the internal surface to the external surface.

15. The process of claim 13 wherein the main body portion has six longitudinally extending preferential tear lines formed therein.

16. The process of claim 13 wherein the first polymeric material is selected from the group consisting of polyethylene, polytetrafluoroethylene and polyurethane.

17. The process of claim 16 wherein the second polymeric material is selected from the group consisting of nylon, silicone thermoplastic copolymer, styrene-butadiene copolymer, polypropylene and styrene ethylene butadiene styrene coplymer.

18. The medical device of claim 13 wherein the first cohesive strength and the second cohesive strength are each higher than the adhesive strength and the first polymeric material and the second polymeric material each have similar melt and flow properties.

19. The medical device of claim 13 wherein the second cohesive strength is less than both the first cohesive strength and the adhesive strength and the first polymeric material and the second polymeric material each have similar melt and flow properties.